examples enhance

* utils for products generator

* load test for each *.test.js file in packages folder

* [test] unit test for utils/common

* refactor all products with productGenerator for all examples

* refactor folder structure

* move component <Code /> to src/components/common
* rename component file name

packages/react-bootstrap-table2-example/src/utils/common.js

@@ -0,0 +1,21 @@
+/**
+ * products generator for stories
+ * 
+ * @param {Number} quantity - quantity of products
+ * @param {Function} callback - callback func which is similiar to 'mapFunction'
+ * aims to customize product format
+ * 
+ * @return {Array} - products array
+ */
+export const productsGenerator = (quantity = 5, callback) => {
+  if (callback) return Array.from({ length: quantity }, callback);
+
+  // if no given callback, retrun default product format.
+  return (
+    Array.from({ length: quantity }, (value, index) => ({
+      id: index,
+      name: `Item name ${index}`,
+      price: 2100 + index
+    }))
+  );
+};